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3.8 8.2 Photosynthesis PPT
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  • Photosynthesis title, definition and equation.
  • Chloroplast: colour TEM, parts and functions.
  • Why does a leaf look green?
  • Action spectrum of photosynthesis shows wavelengths used for light dependent reactions. Different colours are different wavlengths. The green region is not used, so green light is reflected and seen.
  • Absorption spectrum of chlorophyll a vs action spectrum of photosynthesis. Chlorophyll b is used to ‘fill the gaps’ in the action spectrum.
  • Photolysis of water produces high-energy electrons, H+ protons and oxygen.
  • Protons are pumped into stroma using energy from electrons
  • Photosystem I is activated
  • Non-cyclic phosphorylation produces ATP.
  • Reduction of NADP+ by ferredoxin.
  • Calvin cycle overview.
  • Calvin cycle animation links.
  • Team analogy for the limiting factors theory. Time to vote off the weakest link.
  • CO2 affects rate of photosynthesis. CO2 is the substrate in carbon fixation (Calvin cycle) – rubisco is the enzyme.
  • Light intensity affects rate of photosynthesis.
  • Temperature affects the rate of photosynthesis. Remember enzyme theory. Enzymes used in respiration: rubisco is the main one. ATP synthase can also be denatured.
  • Explain the effects of limiting each of the three factors on the process of photosynthesis. It’s not enough to just say “it slows down.”
  • This graph suggests that CO2 is more important than temperature. Why?
  • Iron is limiting – seeding algae with iron stimulates algal blooms. Iron is used in ferroxidase – responsible for reduction of NADP+ in the light dependent reactions. Results with CO2 were short-term. Levels dropped in the immediate area, but the seeding is too expensive to work. Pros: possible reduced CO2 levels, algal blooms provide food for grazers and thus fisheries. Cons: large blooms block light to lower levels, may cause eutrophication; Diatoms block gills of some species; iron seeding may encourage blooms of toxic algae; who owns the ocean?

Transcript

  • 1. Topics 3.8 + 8.2 Photosynthesis
    IB Biology
  • 2.
  • 3. Leaves
    Green tissue in the interior of the leaf (mesophyll) = contains chloroplasts
    CO2 enters the leaf and O2 exits through the stoma
    Stomata =bottom of leaf
  • 4. Chloroplasts
    similar to mitochondria
    outer and inner membrane
    membranous sacs: THYLAKOIDS
    thylakoids = concentrated in stacks called GRANA
    thylakoids: contain chlorophyll (capture light)
    filled with fluid: STROMA (where sugars are made from CO2 )
  • 5. Overview
  • 6. Electromagnetic Spectrum
  • 7.
  • 8.
  • 9.
  • 10. The 2 stages of Photosynthesis
    Light Dependent Reactions:
    convert light energy to chemical energy (ATP + NADPH) and produce oxygen gas as a waste product
    Light Independent Reactions (Calvin Cycle):
    make sugar using carbon dioxide and the energy-containing products of the light-reactions (ATP + NADPH)
  • 11. Light Dependent Reaction
    Light can be..
    Absorbed
    Reflected
    Transmitted
    Occurs in thylakoids
    Chlorophyll A and B = main photosynthetic pigments (also carotenes, anthocyanins)
  • 12. Light Dependent Reaction
    Light energy is used to split water.
    H + is released = used by ATP Synthase to produce ATP
    NADP + is reduced to NADPH+
    ATP and NADPH = used in light independent reactions
    O2 = waste product
  • 13. Photosystems
    Photosystem: place in thylakoid where light is harvested
    Photon is absorbed by a pigment molecule = electrons gain energy
    Excited electron is passed to a neighboring molecule - the primary acceptor
  • 14. Photosystems I & II work together
    Both photosystems absorb light
    Electron Transport Chain= electrons go down an energy hill = lose energy at each step - this energy is stored in ATP or NADPH
    Electrons released from PSI is replaced by electrons coming from PSII
  • 15.
  • 16.
  • 17.
  • 18. Chemiosmosis/Photophosphorylation
  • 19.
  • 20. Role of Water
    The light energy is used to split water molecules (photolysis)
    H2O -> H+ + O + e-
    • The electrons allow reduction of NADP+ / replace those leaving photosystem II
    • 21. H + flow allows ATP production
    • 22. The O2 is released and leaves the plant through the stoma
  • Mechanical Analogy for Making ATP
    As electrons skip down the ETC, ATP are generated.
  • 23. Animations
    http://www.youtube.com/watch?v=hj_WKgnL6MI
  • 24. Light Independent Reaction (Calvin Cycle)
    Glucose phosphate is produced = stored as starch
    CO2 , ATP and NADPH are used
  • 25.
  • 26. Simple Calvin Cycle animations:
  • 27. Summary
    Light dependent reaction
    Light independent reaction
  • 28.
  • 29.
  • 30. plateau
    CO2 is a substrate in an enyme-catalysed light-dependent reaction.
    At low CO2 concentration, rate is positively correlated with concentration
  • 31. plateau
    At low light intensity, rate of photosynthesis is proportional to light intensity.
  • 32. Optimum temperature
    Increased temp. gives increased energy and increased rate of photosynthesis
    Above the optimum temp., enzymes are denatured and rate drops steeply.
  • 33.
  • 34. What are the conditions of each of these trials?
    Rate of photosynthesis
    Light intensity